Packaging sleeves of polygonal cross-section ("polygonal packaging sleeves"), especially such having a rectangular or square cross-section, provide very substantial advantages as compared with conventional circular packaging sleeves, such as savings in space, improved stackability (as rolling away is avoided), avoiding of a bulk freight extra charges, etc.
Packaging sleeves which not only have a polygonal cross-section, but which, moreover, are adapted to be folded at their longitudinal edges, and so may assume a flat state in their empty condition, further substantially reduce the space required in their empty condition, namely to about 1/11 of the polygonal cross-section to which they can be expanded. Owing to this advantage, collapsible or foldable packaging sleeves may be sent in their empty condition to geographically remote markets, making greater production units possible and storage greatly simplified. Besides, certain other operations (hole punching, etc.) can be performed more readily when the sleeves are in the flattened condition.
In the proposed method of production according to the parent application No. 579,058, a positive co-rotation of the shaping tools, i.e. of the mandrel or spindle shaping the polygonal cross-section and, optionally, simultaneously pressing longitudinal grooves into the sleeve wall, may place certain limitations on increases in the rate of production. Besides, easy rotatability of the shaping mandrel requires a more complicated apparatus than might a fixed, or non-rotating mandrel. Further, spiral wrapping or winding operations frequently require a different feeding power than for the shaping into the polygonal cross-section.
The present invention comprises methods of producing a collapsibly foldable packaging sleeve of a polygonal cross-section whereby circular or tubular sleeve stock is formed on a stationary spindle or mandrel from a plurality of glued thin layers of paper, fabric, plastic material or the like, wound or wrapped one over the other. The sleeve is thereafter shaped into a polygonal cross-section. During the shaping of the tubular packaging sleeve in the glue-wetted state, at least one continuous folding edge is impressed into the sleeve wall extending in the longitudinal direction of said sleeve and is press-formed at the desired longitudinally extending edge corners of the polygonal cross-section. This invention is also embodied in an apparatus for carrying out such methods including a stationary wrapping spindle or mandrel upon which the wrapping material may be wound or wrapped, which joins a second mandrel for coaxially receiving said sleeve and which continuously forces said sleeve into the polygonal configuration by enlarging its cross-sectional area, said mandrel being equipped with at least two opposing series or rows of grooving rollers, the projected center planes of which intersect the axis of the second mandrel and which grooving rollers each have an edge impressed into the sleeve wall; said grooving rollers diverging outwards, sequentially from the starting end of said second or polygonally shaping mandrel for a distance such that they reach a radial spacing relative to each other corresponding approximately to the interior diagonal lines of the desired polygonal cross-section.
By means of this method, the sleeve wall may be wound or wrapped in the form of continuous, spirally wrapped sleeve stock which is divided into individual lengths of sleeve, or the sleeve wall may be wound transversely in parallel fashion such that sleeve sections of limited length are formed.
Accordingly, it is the object of the present invention to avoid or minimize prior art limitations and, more particularly, to provide not only improved production, but also means for producing a wide variety of packaging sleeves, while at the same time simplifying the tools used and producing a flattened sleeve in a single operation.